# Tagged Questions

Time series are data observed over time (either in continuous time or at discrete time periods).

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### Seasonal ARIMA for each weekday instead of double seasonal ARIMA

I have read some papers on forecasting time series with double seasonality (e. g. hourly data with daily and weekly seasonality). I understand that double seasonal ARIMA can be used for that purpose. ...
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### Running Linear Regression Model

my question is can i run linear regression model using summarized counts/frequencies? For example, my dependent variable is total number of people who is aware of a specific TV show and my independent ...
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### Detect increase/decrease events on time series

Given a time series, I have to detect two types of events: 1) "medium" decrease 2) "high" increase Event detection should be "fast enough". I used quotation marks as I'd like to set different ...
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### Normalizing year data

I have a data set in which there are data from April 2010 to Dec 2010 ( 9 Months) Jan 2011 to Dec 2011 (12 Months ) Jan 2012 to Dec 2012 (12 Months) Jan 2013 to Dec 2013 (12 Months) Jan 2014 to ...
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### Contradiction in the ADF (Augmented Dickey-Fuller) and KPSS (Kwiatkowski–Phillips–Schmidt–Shin) tests for financial time series

I use the ADF and KPSS to test for stationarity / non-stationarity of price increments in financial time series. The two test applied provide different results for low lags, but the same result for ...
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### Predicting time series value given a threshold weight

I have 2 datasets. One is time series data of sale of homes by region by type: ...
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### Identify outlier usage intervals in time-series data

I want to find outliers in power consumption in real-time, at hourly rate, i.e., at the end of the hour, I should say whether power consumption in current hour was outlier/anomalous or not. Approach: ...
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### VAR lag length vs Johansen cointegration test outcome?

First puzzle: I am taught that the lag order of VECM does not affect the cointegration rank because the lag order is for the differenced regressors. But, I see the contrary: I experimented with sample ...
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### Prewhitening Regressors in Lagged Time Series Regression

I'm trying to identify significant lags in a time series regression such that $Y = \beta_0X_t + \beta_1X_{t-1} + ... + \beta_iX_{t-i} + \alpha_0Z_t + \alpha_1Z_{t-1} + ... + \alpha_jZ_{t-j}$ I ...
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### Maximum Likelihood estimation and the Kalman filter

I know the Kalman filter recursions and can derive these but what I don't really get is how to estimate the hyper parameters using maximum likelihood. I understand that when running the Kalman filter ...
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### Scaling predictors in ARIMA model

If a predictor in an ARIMA model has much lower magnitude than the variable you are trying to predict, then do you need to multiply it by a scalar in order for it to be an effective predictor in the <...
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### Why do VAR forecasted values radically change depending on which month historical data end?

I am building a model to forecast housing variables using vector autoregression. I am encountering spurious results. My forecasted values change dramatically depending in which month the historical ...
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### Negatively Correlated Predictors in Arima Model

If a predictor is negatively correlated with a variable you are trying to forecast in an Arima model, will Arima pick up the negative correlation when you add the predictor in the xreg argument? Is ...
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### Combining Lower Correlation Predictors to Create Higher Correlation Predictors

I'm working on an Arima model to forecast a given variable and so I'm looking in my data for variables with correlation to the variable I'm trying to predict, to add as predictors in the xreg argument....
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### Does picking randomly from an imbalanced group balance the group?

If I had a bag of marbles with 75% blue and 25% red (ratio is what matters not raw number, so this applies to 100 marbles, 1000 marbles, 100000 marbles) So if I had this imbalance of 75% blue and 25% ...
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### Difference between SUTSE (Seemingly Unrelated Time Series Equations) and SUR (Seemingly Unrelated Regressions)

I am studying time-series econometrics and in particular Dynamic Linear Models for multivariate time-series. Someone can help me in understanding which is the difference between SUTSE (Seemingly ...
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### Lag-free filter methods for time series

I'm currently working with accelerometer based raw data (100 hz). Now I want to low pass filter this timeseries of accelerations for further analyses. I tried different filters like the simple moving ...
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### General-to-specific subset selection (“Autometrics”) performing well in macroeconomics

I wonder why general-to-specific (GETS) subset selection and particularly the Autometrics algorithm are performing well in macroeconomic modelling/forecasting. How does Autometrics work? Doornik "...
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### How we can find trend of time series and turning points?

I want something like this in a time series: Currently I'm using some linear interpolation to find trend and turning points. What other methods can I use to find these turning points in a time ...
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### What is Maximal Lyapunov exponent and how to calculate and interpret it in R?

I was researching about chaotic time series and came across Maximal Lyapunov exponent. I tried to read many articles regarding it but the only thing I understood about MLE is this is used to check ...
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### Regression result for second model still shows insignificant variables

I run a regression for my study. I used a quarterly data included 33 number of observations. my problem is independent variables are significant but not perfectly significant. when i run a ...
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### Time-varying predictive model for a set of proportions

Suppose there is a casino where people bet on a weekly horse race. On Sunday, the casino publishes the prices for a wager on each horse for the upcoming Saturday's race. Everyone who wagers on the ...